The present invention relates to a technique for improving controllability of output power using a power control signal in a high-frequency power amplifier circuit and for calibrating variation or dispersion in a characteristic thereof due to deviation of a gain of an amplifier control loop, and in particular, to a technique effectively applicable to a communication semiconductor integrated circuit including a phase detecting or detector circuit and an amplifier detecting circuit and to a wireless or radio communication apparatus such as a portable telephone including the wireless communication apparatus.
One of the systems for wireless communication apparatuses (mobile communication apparatuses) such as a portable telephone of the prior art is a global system for mobile communication (GSM) adopted in Europe. This system uses a phase modulation method called a Gaussian Minimum Shift Keying (GMSK) method in which a phase of a carrier wave or a carrier signal is shifted according to transmission data.
In general, a transmission output section of a wireless communication apparatus includes a high-frequency power amplifier circuit, and some GSM wireless communication apparatuses of the prior art are configured as below. To obtain output power required for a telephone call, a bias voltage of the high-frequency power amplifier is controlled by a control voltage outputted from a circuit called “automatic power control (APC) circuit” which generates a control signal of transmitting or transmission power according to a signal from a detector to detect transmitting or transmission power and a transmission request level from a baseband LSI.
Incidentally, for recent portable telephones, a system of enhanced data rates for GSM evolution (EDGE) has been proposed, the EDGE system having a dual-mode communicating function in which an audio signal is communicated in the GMSK modulation and data is communicated in 3π/8 rotating 8-PSK (phase shift keying) modulation. The 8-PSK modulation is a modulation implemented by adding, for example, amplitude shift to the carrier phase shift of the GMSK modulation. In comparison with the GMSK modulation in which information of one bit is transmitted per symbol, information of three bits is transmitted per symbol in the 8-PSK modulation. Therefore, a higher transmission rate can be used for communication in the EDGE than in the GSM.
As a method to implement a modulation method in which each of a phase component and an amplitude component of a transmitting or transmission signal contain information, there has been heretofore known a method called “polar loop” in which a signal to be transmitted is divided into a phase component and an amplitude component, a feedback operation is conducted for the components respectively by a phase component loop and an amplitude component loop, and signals resultant from the feedback operations are mixed with each other by an amplifier to output a signal (described, for example, in page 162 of “High Linearity RF Amplifier Design” written by Peter B. Kenington and published from ARTECH HOUSE, INC. in 1979).
Since it is necessary in the GSM communication system to output a phase-modulated signal according to a requested output level, a high-frequency power amplifier circuit in a final stage can be operated in a saturation range. In contrast therewith, in a wireless communication system capable of conducting communication in the EDGE method, the high-frequency power amplifier circuit in the final stage must be operated in a non-saturation range. However, in a drive method to drive a high-frequency power amplifier circuit used in the GSM communication system of the prior art, it is difficult to keep linearity required for the high-frequency power amplifier circuit in a region of a low output level. In comparison with this method, the polar loop method is advantageous: the request of linearity for the high-frequency power amplifier circuit can be satisfied and power efficiency in a low output level range can also be improved.